diff --git a/LICENSE.txt b/LICENSE.txt
index e83d6e64b..3ccff7b2a 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -1,4 +1,4 @@
-Copyright (c) 2015 John Kerl
+Copyright (c) 2015- John Kerl
 
 All rights reserved.
 
diff --git a/c/cli/argparse.h b/c/cli/argparse.h
index 6cf82d643..a0355ecf6 100644
--- a/c/cli/argparse.h
+++ b/c/cli/argparse.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Argument-parsing library, with non-getopt semantics.
+// ================================================================
+
 #ifndef ARGPARSE_H
 #define ARGPARSE_H
 #include "containers/slls.h"
diff --git a/c/cli/mlrcli.h b/c/cli/mlrcli.h
index 65c095864..e4a5c5e02 100644
--- a/c/cli/mlrcli.h
+++ b/c/cli/mlrcli.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Miller command-line parsing
+// ================================================================
+
 #ifndef MLRCLI_H
 #define MLRCLI_H
 
diff --git a/c/containers/header_keeper.h b/c/containers/header_keeper.h
index 74f617228..6fb7bc4d4 100644
--- a/c/containers/header_keeper.h
+++ b/c/containers/header_keeper.h
@@ -1,10 +1,13 @@
+// ================================================================
+// Retains field names from CSV header lines across record reads.
+// See also c/README.md.
+// ================================================================
+
 #ifndef HEADER_KEEPER_H
 #define HEADER_KEEPER_H
 
 #include "containers/slls.h"
 
-// xxx cmt w/ xref
-
 typedef struct _header_keeper_t {
 	char*   line;
 	slls_t* pkeys;
diff --git a/c/containers/hss.h b/c/containers/hss.h
index 6c2ea2785..c8db570db 100644
--- a/c/containers/hss.h
+++ b/c/containers/hss.h
@@ -1,6 +1,3 @@
-#ifndef HSS_H
-#define HSS_H
-
 // ================================================================
 // Array-only (open addressing) string-valued hash set with linear probing for
 // collisions.
@@ -13,6 +10,9 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef HSS_H
+#define HSS_H
+
 // ----------------------------------------------------------------
 typedef struct _hsse_t {
 	char* key;
@@ -28,6 +28,7 @@ typedef struct _hss_t {
 	hsse_t* array;
 } hss_t;
 
+// ----------------------------------------------------------------
 hss_t* hss_alloc();
 void   hss_free(hss_t* pset);
 void   hss_add(hss_t* pset, char* key);
diff --git a/c/containers/join_bucket_keeper.h b/c/containers/join_bucket_keeper.h
index f547c81f1..b2df8fcbb 100644
--- a/c/containers/join_bucket_keeper.h
+++ b/c/containers/join_bucket_keeper.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Data structures for mlr join
+// ================================================================
+
 #ifndef JOIN_BUCKET_KEEPER_H
 #define JOIN_BUCKET_KEEPER_H
 
diff --git a/c/containers/lhms2v.h b/c/containers/lhms2v.h
index bc1cb4928..fc3364d7f 100644
--- a/c/containers/lhms2v.h
+++ b/c/containers/lhms2v.h
@@ -1,8 +1,3 @@
-#ifndef LHMS2V_H
-#define LHMS2V_H
-
-#include "containers/slls.h"
-
 // ================================================================
 // Array-only (open addressing) string-pair-to-void-star linked hash map with
 // linear probing for collisions.
@@ -18,6 +13,9 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef LHMS2V_H
+#define LHMS2V_H
+
 // ----------------------------------------------------------------
 typedef struct _lhms2ve_t {
 	int   ideal_index;
diff --git a/c/containers/lhmsi.h b/c/containers/lhmsi.h
index 6b39b37af..4deaed1a9 100644
--- a/c/containers/lhmsi.h
+++ b/c/containers/lhmsi.h
@@ -1,8 +1,3 @@
-#ifndef LHMSI_H
-#define LHMSI_H
-
-#include "containers/sllv.h"
-
 // ================================================================
 // Array-only (open addressing) string-to-int linked hash map with linear
 // probing for collisions.
@@ -18,6 +13,9 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef LHMSI_H
+#define LHMSI_H
+
 // ----------------------------------------------------------------
 typedef struct _lhmsie_t {
 	int   ideal_index;
diff --git a/c/containers/lhmslv.h b/c/containers/lhmslv.h
index 88ca90bc5..91a3a6a09 100644
--- a/c/containers/lhmslv.h
+++ b/c/containers/lhmslv.h
@@ -1,8 +1,3 @@
-#ifndef LHMSLV_H
-#define LHMSLV_H
-
-#include "containers/slls.h"
-
 // ================================================================
 // Array-only (open addressing) string-list-to-void-star linked hash map with
 // linear probing for collisions.
@@ -18,6 +13,11 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef LHMSLV_H
+#define LHMSLV_H
+
+#include "containers/slls.h"
+
 // ----------------------------------------------------------------
 typedef struct _lhmslve_t {
 	int   ideal_index;
diff --git a/c/containers/lhmss.h b/c/containers/lhmss.h
index 607e5a38c..0cd5bd43f 100644
--- a/c/containers/lhmss.h
+++ b/c/containers/lhmss.h
@@ -1,8 +1,3 @@
-#ifndef LHMSS_H
-#define LHMSS_H
-
-#include "containers/sllv.h"
-
 // ================================================================
 // Array-only (open addressing) string-to-string linked hash map with linear
 // probing for collisions.
@@ -18,6 +13,11 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef LHMSS_H
+#define LHMSS_H
+
+#include "containers/sllv.h"
+
 // ----------------------------------------------------------------
 typedef struct _lhmsse_t {
 	int   ideal_index;
diff --git a/c/containers/lhmsv.h b/c/containers/lhmsv.h
index c12dc225f..3a1a6355f 100644
--- a/c/containers/lhmsv.h
+++ b/c/containers/lhmsv.h
@@ -1,8 +1,3 @@
-#ifndef LHMSV_H
-#define LHMSV_H
-
-#include "containers/sllv.h"
-
 // ================================================================
 // Array-only (open addressing) string-to-void linked hash map with linear
 // probing for collisions.
@@ -18,6 +13,11 @@
 // * http://docs.oracle.com/javase/6/docs/api/java/util/Map.html
 // ================================================================
 
+#ifndef LHMSV_H
+#define LHMSV_H
+
+#include "containers/sllv.h"
+
 // ----------------------------------------------------------------
 typedef struct _lhmsve_t {
 	int   ideal_index;
diff --git a/c/containers/mixutil.h b/c/containers/mixutil.h
index a02116058..d88680aa0 100644
--- a/c/containers/mixutil.h
+++ b/c/containers/mixutil.h
@@ -1,4 +1,7 @@
+// ================================================================
 // Functions involving more than one container type
+// ================================================================
+
 #ifndef MIXUTIL_H
 #define MIXUTIL_H
 #include "containers/lrec.h"
diff --git a/c/containers/mlr_dsl_ast.h b/c/containers/mlr_dsl_ast.h
index dada232e0..2b2e2ac53 100644
--- a/c/containers/mlr_dsl_ast.h
+++ b/c/containers/mlr_dsl_ast.h
@@ -1,11 +1,11 @@
-#ifndef MLR_DSL_AST_H
-#define MLR_DSL_AST_H
-#include "sllv.h"
-
 // ================================================================
 // Miller abstract syntax tree for put and filter.
 // ================================================================
 
+#ifndef MLR_DSL_AST_H
+#define MLR_DSL_AST_H
+#include "sllv.h"
+
 #define MLR_DSL_AST_NODE_TYPE_LITERAL          0xaaaa
 #define MLR_DSL_AST_NODE_TYPE_FIELD_NAME       0xbbbb
 #define MLR_DSL_AST_NODE_TYPE_FUNCTION_NAME    0xcccc
diff --git a/c/containers/percentile_keeper.h b/c/containers/percentile_keeper.h
index 0d10bf6e8..f737c5adc 100644
--- a/c/containers/percentile_keeper.h
+++ b/c/containers/percentile_keeper.h
@@ -1,9 +1,11 @@
+// ================================================================
+// For mlr stats1 percentiles
+// ================================================================
+
 #ifndef PERCENTILE_KEEPER_H
 #define PERCENTILE_KEEPER_H
 #include "containers/lrec.h"
 
-// For mlr stats1 percentiles
-
 typedef struct _percentile_keeper_t {
 	double* data;
 	int     size;
diff --git a/c/containers/slls.h b/c/containers/slls.h
index a37869b8f..a3f1ddf61 100644
--- a/c/containers/slls.h
+++ b/c/containers/slls.h
@@ -1,4 +1,7 @@
+// ================================================================
 // Singly linked list of string, with tail for append.
+// ================================================================
+
 #ifndef SLLS_H
 #define SLLS_H
 
diff --git a/c/containers/sllv.h b/c/containers/sllv.h
index 90708dc67..c50277406 100644
--- a/c/containers/sllv.h
+++ b/c/containers/sllv.h
@@ -1,4 +1,7 @@
+// ================================================================
 // Singly-linked list of void-star, with tail for append.
+// ================================================================
+
 #ifndef SLLV_H
 #define SLLV_H
 
diff --git a/c/containers/top_keeper.h b/c/containers/top_keeper.h
index 3aa3f3987..c657c8a9c 100644
--- a/c/containers/top_keeper.h
+++ b/c/containers/top_keeper.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Data structure for mlr top: just a decorated array.
+// ================================================================
+
 #ifndef TOP_KEEPER_H
 #define TOP_KEEPER_H
 #include "containers/lrec.h"
diff --git a/c/input/file_reader_mmap.h b/c/input/file_reader_mmap.h
index 648064efe..3a3fbce9e 100644
--- a/c/input/file_reader_mmap.h
+++ b/c/input/file_reader_mmap.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Abstraction layer for mmapped file-read logic.
+// ================================================================
+
 #ifndef FILE_READER_MMAP_H
 #define FILE_READER_MMAP_H
 
diff --git a/c/input/file_reader_stdio.h b/c/input/file_reader_stdio.h
index 24a5a6a95..f313dadaf 100644
--- a/c/input/file_reader_stdio.h
+++ b/c/input/file_reader_stdio.h
@@ -1,3 +1,7 @@
+// ================================================================
+// Abstraction layer for stdio file-read logic.
+// ================================================================
+
 #ifndef FILE_READER_STDIO_H
 #define FILE_READER_STDIO_H
 
diff --git a/c/lib/minunit.h b/c/lib/minunit.h
index 9aca34e45..ba3c373e2 100644
--- a/c/lib/minunit.h
+++ b/c/lib/minunit.h
@@ -1,6 +1,8 @@
+// ================================================================
 // http://www.jera.com/techinfo/jtns/jtn002.html
 // MinUnit license:
 // "You may use the code in this tech note for any purpose, with the understanding that it comes with NO WARRANTY."
+// ================================================================
 
 #ifndef MINUNIT_H
 #define MINUNIT_H
diff --git a/c/lib/mlrmath.h b/c/lib/mlrmath.h
index 843b85578..742bea835 100644
--- a/c/lib/mlrmath.h
+++ b/c/lib/mlrmath.h
@@ -9,6 +9,7 @@ void mlr_get_real_symmetric_eigensystem(
 	double  eigenvector_2[2]); // Output: corresponding to less-dominant eigenvalue
 
 double qnorm(double x);
+
 double invqnorm(double x);
 
 #endif // MLRMATH_H
diff --git a/c/todo.txt b/c/todo.txt
index 2301a5cd0..09b8bc60f 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -14,9 +14,6 @@ TOP OF LIST
 
 * doc w/ very specific examples of sed/grep/etc preprocessing to structurize semi-structured data (e.g. logs)
 
-!! join: cleanup of xxx cmts
-
-!! mmap cleanup, especially csv
 ! doc stats1/stats2 accums via then-statements ...
 
 !! update t1.rb including numeric sort; fix appropriateness of -t=
@@ -123,6 +120,12 @@ UT/REG
 * mmap/stdio UTs; run all cases with --mmap and again with --no-mmap
 * all __X_MAIN__ instances -> UT code (effectively all-but-dead code at present)
 
+================================================================
+HYGIENE
+
+!! join: cleanup of xxx cmts
+!! mmap cleanup, especially csv
+
 ================================================================
 HARDER HYGIENE
 * eliminate compiler warnings for lemon & its autogenerated code